My late 2010 A5 Cabriolet 3.0TDi Quattro that I purchased in May this year and has now clocked up 133,000 miles is a perfect example of a fabric roof that is wearing as it should!
I think because of the lining inside the outer fabric creases probably more than some cars.
Having said that the material is robust and though it shows signs of wear and tear is nowhere near worn out!
The hydraulic pump and rams would appear robust and remarkably quiet in operation.
So if considering buying a cabriolet, take it on a test drive and find a nice quiet lay-by and raise and lower the roof a few times, listening for any whines and graunching, as it should be smooth and quiet.
Stop it half way and check that it carries on opening or closing smoothly from a standstill.
It is quite a heavy structure but the hydraulics should cope easily.
There are plenty of products on the market for smartening up ageing fabric roofs. A bit of TLC using a cleanser and proofer will help the fabric maintain the suppleness it started life with as well keeping it nice and water resistant.
Power washing is a no no! A bit of elbow grease and a softish scrubbing brush will be all you need, keep the power washing for the wheel arches!
If after a couple of years use and you are unlucky and it does fray, then there are plenty of specialist places that can replace the fabric and sort out mechanical issues at way below Audi prices.
Bearing in mind they are working on convertibles every day their working lives their expertise is far greater than an Audi trained mechanic who could well have been shown how to do it, but would have forgotten how as he probably has never had to replace one!!
Best
Ian